Western Pennsylvania becomes a political litmus test on Monday when Vice President Joe Biden visits Pittsburgh to take part in Labor Day festivities.

The 72-year-old Democrat from Delaware has been coy about his presidential aspirations, but political analysts see his visit as a test of Biden’s viability as alternative to front-runner Hillary Clinton. Her campaign is bogged down over questions about a personal e-mail server she had while serving as secretary of state.

In Pittsburgh, Biden will march with AFL-CIO President Richard Trumka and about 60,000 labor union members and their supporters.

Biden’s path to the presidency is a narrow one. As vice president, he must remain supportive and consistent with the policies of President Barack Obama.

That’s one of the reasons he spoke passionately Thursday in defense of Obama’s Iran nuclear agreement, which faces a congressional attempt to block it.

“I tell you, I firmly believe, and I will go into some detail here, it will make us and Israel safer, not weaker,” Biden said at a round-table discussion.

Another participant in that discussion was U.S. Rep. Debbie Wasserman Schultz, D-Fla., chair of the Democratic National Committee. Wasserman Schultz has not said how she will vote on the Iran agreement.

For Biden, there’s safety in the perception that he’s the most logical heir to an Obama presidency. Candidate Biden would be expected to maintain most of Obama’s policies and objectives.

Clinton does not fit that template. She was never seen as an Obama acolyte, even while serving on his Cabinet. Before Obama appointed Clinton secretary of state — an appointment now mired in controversy over her personal e-mail server — she was Obama’s political rival for the 2008 presidential election.

Presenting himself as an Obama protégé will score huge points for Biden with the Labor Day crowd. Obama has done more for the struggling labor movement than any president since Jimmy Carter.

Obama’s Democratic appointees to the National Labor Relations Board have issued a series of rulings that favor unions, according to Politico, including six pro-labor decisions in just the past few days. On Thursday, the NLRB issued a ruling that could make it easier for McDonald’s employees to unionize, reversing a 34-year precedent.

On Monday, Biden will be looking for commitments from the organized labor community. And they will be seeking commitments from Biden.

What’s likely is an alliance that propels Biden into the race and possibly into the White House in 2016.

It’s likely to be a fun and colorful event, even for those who don’t follow presidential politics.

The Allegheny County Labor Day Parade will begins at 10 a.m. at Liberty Avenue and Grant Street and will proceed along Grant to the Boulevard of Allies to the United Steelworkers of America building.